Polyimide resins and polybenzoxazole resins having excellent heat resistance, electrical characteristics and mechanical characteristics or the like have been used for surface protection films and interlayer insulating films of a semiconductor element (Patent Document 1).
However, when a polyimide resin has been used, there exists a problem in that a polyamide acid, which is a precursor before curing, has caused the copper used for wiring to corrode, and as a result, migration has occurred. Also, the polyimide resin has a high cure temperature of about 350° C., and therefore there is a problem that the copper has been oxidized in the cure reaction.
Furthermore, the high integration and multilayering of a semiconductor element which is represented by the semiconductor device having a wafer level package structure has caused large problems such as the delay of signals in the wiring and the increase of power consumption. Since the polyimide resin has a comparatively high dielectric constant of 2.6 to 3.5, materials having a low dielectric constant have been required for the surface protection films and the interlayer insulating films.
In addition, there exists a problem in that both the polyimide resin and the polybenzoxazole resin have had large stress. When these resin layers have been used in the frontier semiconductor, a problem exists in that the semiconductor element has been broken because of the stress of the protective film itself, and the stress from the outside has not been able to be reduced. Thereby, lower stress properties have been required for the protective film.
The resin composition used for the semiconductor device having the wafer level package structure for solving the above problems has not been known until now.
Patent Document 1: Japanese Patent Laid-Open No. 2001-194796